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Avalanche Forecast

Archived

Nov 25th, 2012–Nov 26th, 2012

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast.

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the forecaster's blog for further details on interpreting early season bulletins.

Confidence

Poor - Due to limited field observations

Weather Forecast

Synopsis: A ridge of high pressure over southern BC should give mainly sunny skies for Monday and Tuesday. The ridge should break down on Wednesday allowing a mild frontal system to push in. Monday: A mix of sun and cloud. Freezing level near surface with a potential above freezing layer developing. Winds are light and variable. Tuesday: A mix of sun and cloud. Freezing level at around 2300 m. Winds light from the northwest. Wednesday: Increasing cloud with precipitation developing. Freezing level around 1800 m.

Avalanche Summary

There are no new reports from the region. Natural avalanche activity was likely during the storm on Friday and Saturday morning. Cooler and drier conditions should decrease the likelihood of natural activity, but human triggered avalanche remain possible, particularly on exposed wind loaded slopes and cross-loaded gullies.

Snowpack Summary

Recent storm snow has probably settled and strengthened under cooler temperatures. Dense wind slabs may still be susceptible to triggering in steep lee terrain. The main snowpack feature is a rain crust buried early November and now down around 80cm at treeline. A weak layer of facets sitting on top of this crust shows "collapse" fracture character and the ability to propagate. Widespread whumpfing and cracking on this layer has also been reported. It's mostly a concern at upper treeline and alpine elevations on slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, grass, etc.). Coquihalla Pass has 100 cm on the ground, and Cayoosh Pass has about 50cm. Treeline areas have around 100-120 cm, and alpine areas likely have more snow, but also highly variable depths depending on wind exposure. For more information check out the telemarktips.com forum, the Mountain Conditions Report, and Wayne Flann's Avalanche Blog.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.